In electro-optical devices such as a liquid crystal display device and an organic EL (Electro Luminescence) display device and so on, a thin film circuit including a thin film transistor as a semiconductor element is used to implement switching a pixel element and so on. With a conventional thin film transistor, an amorphous silicon film is used to form active regions such as a channel forming region and so on. Meanwhile, a thin film transistor, in which active regions are formed by using a polycrystalline silicon film, is also put into practical use. In comparison to using an amorphous silicon film, using a polycrystalline silicon film makes it possible to improve electrical characteristics such as mobility and so on, and also to increase performance of the thin film transistor.
Moreover, in order to further improve performance of the thin film transistor; an advanced technique is under consideration to form a semiconductor film composed of larger crystalline grains which prevent a grain boundary from entering the channel forming region of the thin film transistor. For example; a technique has been proposed, in which a minute hole is formed on a substrate and crystallization of the semiconductor film is carried out while the minute hole is used as an origin of crystal growth so that a large-sized silicon crystalline grain is formed. Such a technique is described in Japanese Unexamined Patent Publication No. JP11087243, Literature “Single Crystal Thin Film Transistors”; IBM TECHNICAL DISCLOSURE BULLETIN August 1993 pp. 257–258”, and Literature “Advanced Excimer-Laser Crystallization Techniques of Si Thin-Film For Location Control of Large Grain on Glass”; R. Ishihara et al., proc. SPIE 2001, vol. 4295 pp. 14–23”.
By forming a thin film transistor with a silicon film having a large grain size according to the above-referenced prior art technique, it becomes possible to prevent a grain boundary from entering a forming region (a channel forming region, in particular) of a thin film transistor. Thus, it becomes possible to realize a thin film transistor that is excellent in electrical characteristics such as mobility and so on.